On 01/19/2015 11:45 AM, Thomas Gleixner wrote: > On Fri, 16 Jan 2015, Darren Hart wrote: >> On 1/16/15, 12:54 PM, "Michael Kerrisk (man-pages)" >> <mtk.manpages@xxxxxxxxx> wrote: >> >>> On 01/16/2015 04:20 PM, Thomas Gleixner wrote: >>>> On Fri, 16 Jan 2015, Michael Kerrisk (man-pages) wrote: >>>> >>>>> Hello Thomas, >>>>> >>>>> On 01/15/2015 11:23 PM, Thomas Gleixner wrote: >>>>>> On Thu, 15 Jan 2015, Michael Kerrisk (man-pages) wrote: >>>>>>>> [EINVAL] uaddr equal uaddr2. Requeue to same futex. >>>>>>> >>>>>>> ??? I added this, but does this error not occur only for PI requeues? >>>>>> >>>>>> It's equally wrong for normal futexes. And its actually the same code >>>>>> checking for this for all variants. >>>>> >>>>> I don't understand "equally wrong" in your reply, I'm sorry. Do you >>>>> mean: >>>>> >>>>> a) This error text should be there for both normal and PI requeues >>>> >>>> It is there for both. The requeue code has that check independent of >>>> the requeue type (normal/pi). It never makes sense to requeue >>>> something to itself whether normal or pi futex. We added this for PI, >>>> because there it is harmful, but we did not special case it. So normal >>>> futexes get the same treatment. >>> >>> Hello Thomas, >>> >>> Color me stupid, but I can't see this in futex_requeue(). Where is that >>> check that is "independent of the requeue type (normal/pi)"? >>> >>> When I look through futex_requeue(), all the likely looking sources >>> of EINVAL are governed by a check on the 'requeue_pi' argument. >> >> >> Right, in the non-PI case, I believe there are valid use cases: move to >> the back of the FIFO, for example (OK, maybe the only example?). Both >> tests ensuring uaddr1 != uaddr2 are under the requeue_pi conditional >> block. The second compares the keys in case they are not FUTEX_PRIVATE >> (uaddrs would be different, but still the same backing store). >> >> Thomas, am I missing a test for this someplace else? > > No, I had a short look at the code misread it. So, yes, it's a valid > operation for the non PI case. Sorry for the confusion. Thanks for the confirmation, Thomas. Page updated to remove FUTEX_CMP_REQUEUE from that error case. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
